I am going to make a firebox with flame imitation in it. Logically thinking I have to make a hole inside of my cab. But I have no idea about the diameter. I never have been in steamer cab and never saw a firebox. My Mountain is here - https://www.youtube.com/watch?v=2N6xMrGkLik
There must be 43,000 pics of real and model steam fire doors in the cabs. Search 'how to fire a steam loco', on youtube and myriad of pics in TBoard under several categories. When you see the fire doors get a guesstemate of size of stoking hole and doors. (probably about 2-3' wide X 1.5 - 2' high. Then scale it down to your backhead and as long as nothing will be ruined on the other side, drill/shape a hole. To be authentic you'll need to see glow in ash pans and under cab nearer to last drivers. Maybe more than one bulb/LED in parallel..I've never done this but I think my logic is sound (actually 'light', not sound !).
